Isotope Dilution Alpha Spectrometry Research Articles

New determination of the 229Th half-life.

A new determination of the 229Th half-life was made based on measurements of the 229Th massic activity of a high-purity solution for which the 229Th molality had previously been measured. The 229Th massic activity was measured by direct comparison with SRM 4328C using 4παβ liquid scintillation counting, NaI counting, and standard addition liquid scintillation counting. The massic activity was confirmed by isotope dilution alpha spectrometry measurements. The calculated 229Th half-life is (7825 ± 87) years (k = 2), which is shorter than the three most recent half-life determinations but is consistent with these values within uncertainties.

Chemically selective polymer substrate based direct isotope dilution alpha spectrometry of Pu

Quantification of actinides in the complex environmental, biological, process and waste streams samples requires multiple steps like selective preconcentration and matrix elimination, solid source preparations generally by evaporation or electrodeposition, and finally alpha spectrometry. To minimize the sample manipulation steps, a membrane based isotope dilution alpha spectrometry method was developed for the determination of plutonium concentrations in the complex aqueous solutions. The advantages of this method are that it is Pu(IV) selective at 3M HNO3, high preconcentration factor can be achieved, and obviates the need of solid source preparation. For this, a thin phosphate–sulfate bifunctional polymer layer was anchored on the surface of microporous poly(ethersulfone) membrane by UV induced surface grafting. The thickness of the bifunctional layer on one surface of the poly(ethersulfone) membrane was optimized. The thickness, physical and chemical structures of the bifunctional layer were studied by secondary ionization mass spectrometry (SIMS), scanning electron microscopy (SEM) and SEM–EDS (energy-dispersive spectroscopy). The optimized membrane was used for preconcentration of Pu(IV) from aqueous solutions having 3–4M HNO3, followed by direct quantification of the preconcentrated Pu(IV) by isotope dilution alpha spectrometry using 238Pu spike. The chemical recovery efficiency of Pu(IV) was found to be 86±3% below Pu(IV) loading capacity (1.08μg in 2×1cm2) of the membrane sample. The experiments with single representative actinides indicated that Am(III) did not sorb to significant extent (7%) but U(VI) sorbed with 78±3% efficiency from the solutions having 3M HNO3 concentration. However, Pu(IV) chemical recovery in the membrane remained unaffected from the solution containing 1:1000wt. proportion of Pu(IV) to U(VI). Pu concentrations in the (U, Pu)C samples and in the irradiated fuel dissolver solutions were determined. The results thus obtained were found to be in good agreement with those obtained by conventional alpha spectrometry, biamperometry and thermal ionization mass spectrometry.

Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale.

BackgroundThe economic value of unconventional natural gas resources has stimulated rapid globalization of horizontal drilling and hydraulic fracturing. However, natural radioactivity found in the large volumes of “produced fluids” generated by these technologies is emerging as an international environmental health concern. Current assessments of the radioactivity concentration in liquid wastes focus on a single element—radium. However, the use of radium alone to predict radioactivity concentrations can greatly underestimate total levels.ObjectiveWe investigated the contribution to radioactivity concentrations from naturally occurring radioactive materials (NORM), including uranium, thorium, actinium, radium, lead, bismuth, and polonium isotopes, to the total radioactivity of hydraulic fracturing wastes.MethodsFor this study we used established methods and developed new methods designed to quantitate NORM of public health concern that may be enriched in complex brines from hydraulic fracturing wastes. Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM.ResultsWe observed that radium decay products were initially absent from produced fluids due to differences in solubility. However, in systems closed to the release of gaseous radon, our model predicted that decay products will begin to ingrow immediately and (under these closed-system conditions) can contribute to an increase in the total radioactivity for more than 100 years.ConclusionsAccurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment. These predictions must include an understanding of the geochemistry, decay properties, and ingrowth kinetics of radium and its decay product radionuclides.CitationNelson AW, Eitrheim ES, Knight AW, May D, Mehrhoff MA, Shannon R, Litman R, Burnett WC, Forbes TZ, Schultz MK. 2015. Understanding the radioactive ingrowth and decay of naturally occurring radioactive materials in the environment: an analysis of produced fluids from the Marcellus Shale. Environ Health Perspect 123:689–696; http://dx.doi.org/10.1289/ehp.1408855

A simple-rapid method to separate uranium, thorium, and protactinium for U-series age-dating of materials

Uranium-series dating techniques require the isolation of radionuclides in high yields and in fractions free of impurities. Within this context, we describe a novel-rapid method for the separation and purification of U, Th, and Pa. The method takes advantage of differences in the chemistry of U, Th, and Pa, utilizing a commercially-available extraction chromatographic resin (TEVA) and standard reagents. The elution behavior of U, Th, and Pa were optimized using liquid scintillation counting techniques and fractional purity was evaluated by alpha-spectrometry. The overall method was further assessed by isotope dilution alpha-spectrometry for the preliminary age determination of an ancient carbonate sample obtained from the Lake Bonneville site in western Utah (United States). Preliminary evaluations of the method produced elemental purity of greater than 99.99% and radiochemical recoveries exceeding 90% for U and Th and 85% for Pa. Excellent purity and yields (76% for U, 96% for Th and 55% for Pa) were also obtained for the analysis of the carbonate samples and the preliminary Pa and Th ages of about 39,000 years before present are consistent with 14C-derived age of the material.

Analysis of polonium-210 in food products and bioassay samples by isotope-dilution alpha spectrometry

A rapid and reliable radiochemical method coupled with a simple and compact plating apparatus was developed, validated, and applied for the analysis of 210Po in variety of food products and bioassay samples. The method performance characteristics, including accuracy, precision, robustness, and specificity, were evaluated along with a detailed measurement uncertainty analysis. With high Po recovery, improved energy resolution, and effective removal of interfering elements by chromatographic extraction, the overall method accuracy was determined to be better than 5% with measurement precision of 10%, at 95% confidence level.

Rapid method for the determination of actinides in soil and sediment samples by alpha spectrometry

A rapid procedure for the determination of Am, Pu, Th and U radionuclides in soil and sediment samples is described that can be used for environmental monitoring in emergency situations. The method is based on the fast and complete destruction of small amounts (up to 0.5 g) of samples by lithium metaborate fusion, followed by pre-concentration of the actinides by co-precipitation with calcium fluoride in acidic solution, and separation of the actinides by selective extraction chromatography using a single column filled with TRU resin. Am, Pu and Th are stripped separately, while U and Np are stripped together. Alpha sources are prepared from the chromatographic strip solutions directly by micro-co-precipitation with neodymium fluoride. Activities are determined by means of isotope dilution alpha spectrometry. The method provides accurate and reliable results for the activity concentrations of elevated levels of 239,240 Pu, 238 Pu, 241 Am and natural levels of Th nuclides in soil and sediment samples in course of 24 h. By further purification U and Np nuclides can be separated and determined, too.

Alpha-particle emitters targeted by specific antitumor antibodies

Radionuclidic impurities of 210Po prepared by neutron irradiation of 209Bi via the 209Bi(n,γ)210Bi reaction were investigated. Following irradiation and ingrowth, a pure 210Po solution was obtained by sublimation and dissolution. Results were obtained by liquid scintillation (LS) counting, isotope dilution alpha (α)-spectrometry, and high-purity germanium gamma-ray spectrometry. No alpha-emitting (3–10 MeV) or gamma-emitting (30–3600 keV) impurities were detected, with calculated lower limits of detection for impurities of approximately 0.01% 210Po activity. LS spectra revealed no identifiable beta-emitting impurity. LS sources prepared using Opti-Phase ‘Hi Safe’ III and Opti-Fluor LS cocktails were stable over a 4-day multi-cycle counting period for 210Po dissolved in 0.1% trifluoracetic acid (pH ∼2, water fraction ∼2%). The radioactivity concentration determined by LS counting was verified by isotope dilution alpha spectrometry. These results suggest that neutron irradiation of 209Bi (followed by sublimation) can produce 210Po in a highly pure form that is suitable for radiopharmaceutical preparations.

An assessment of radionuclidic impurities of 210Po produced via neutron irradiation of 209Bi for use in targeted alpha-particle radiotherapy

Radionuclidic impurities of 210Po prepared by neutron irradiation of 209Bi via the 209Bi(n,γ) 210Bi reaction were investigated. Following irradiation and ingrowth, a pure 210Po solution was obtained by sublimation and dissolution. Results were obtained by liquid scintillation (LS) counting, isotope dilution alpha (α)-spectrometry, and high-purity germanium gamma-ray spectrometry. No alpha-emitting (3–10 MeV) or gamma-emitting (30–3600 keV) impurities were detected, with calculated lower limits of detection for impurities of approximately 0.01% 210Po activity. LS spectra revealed no identifiable beta-emitting impurity. LS sources prepared using Opti-Phase ‘Hi Safe’ III and Opti-Fluor LS cocktails were stable over a 4-day multi-cycle counting period for 210Po dissolved in 0.1% trifluoracetic acid (pH ∼2, water fraction ∼2%). The radioactivity concentration determined by LS counting was verified by isotope dilution alpha spectrometry. These results suggest that neutron irradiation of 209Bi (followed by sublimation) can produce 210Po in a highly pure form that is suitable for radiopharmaceutical preparations.

Effect of radioactive decay of Pu isotopes on the determination of Pu concentration with high accuracy by isotope dilution mass spectrometry (IDMS) and isotope dilution alpha spectrometry (IDAS)

Isotope dilution techniques, using a suitable tracer or spike isotope, are commonly used for determining Pu concentration in complex matrices like dissolver solution of irradiated fuel. One of the main reasons for this is the high accuracy achievable due to the elimination of matrix effects present in other analytical techniques. However, the radioactive decay of Pu isotopes in the tracer, if not accounted for, would lead to systematic uncertainty in the results. Taking examples of 240Pu and 238Pu tracers used in our laboratory for isotope dilution mass spectrometry (IDMS) and isotope dilution alpha spectrometry (IDAS), respectively, it is shown that depending upon the isotopic composition of the tracer and the time elapsed after tracer calibration, the radioactive decay could lead to an overall correction factor ranging from 0.1 to about 4% over a period of 5 years. The calculations shown in this work demonstrate the importance of considering radioactive decay, especially when high accuracies are desirable, e.g. in nuclear material accounting.

Assessing the 210At impurity in the production of 211At for radiotherapy by 210Po analysis via isotope dilution alpha spectrometry

A method for assessing the impurity 210At in cyclotron-produced 211At via isotope dilution alpha spectrometry is presented. The activity of 210At is quantified by measuring the activity of daughter nuclide 210Po. Counting sources are prepared by spontaneous deposition of Po on a silver disc. Activity of 210At (at the time of 210Po maximum activity) is found to be 83.5±9.0 Bq, corresponding to an atom ratio ( 210At: 211At at the time of distillation) of 0.010±0.007% ( k = 2 ). The method produces high-quality alpha spectra, with baseline alpha-peak resolution and chemical yields of greater than 85%.

Determination of 241Am in sediments by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS)

Trace levels (pg kg −1) of 241Am in sediments were determined by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS) using a microconcentric nebulizer. 241Am was isolated from major elements like Ca and Fe by different selective precipitations. In further steps, Am was first separated from other transuranic elements and purified by anion exchange and extraction chromatography prior to the mass spectrometric measurements. The ID HR ICP-MS results are compared with isotope dilution alpha spectrometry.

A novel technique for the simultaneous determination of 210Pb and 210Po using a crown ether

A simple radiochemical procedure has been developed to separate lead and polonium simultaneously from different environmental and biological materials. After adding 208Po tracer and lead carrier samples are decomposed using mineral acids. Lead and polonium are selectively retained from 2 m HCl solution by the bis-4,4′(5′)- t-butyl-cyclohexano-18-crown-6-ether; polonium is stripped with 6 m HNO 3 while lead is stripped with 6 m HCL solution. A polonium source is prepared by spontaneous deposition onto a silver disk. The activity concentration of 210Po is determined by isotope dilution alpha spectrometry. Lead is precipitated as oxalate; the chemical recovery is determined by gravimetry. The activity concentration of 210Pb is calculated from the liquid scintillation spectrum.

Well Ge and semi-planar Ge (HP) detectors for low-level gamma-spectrometry

Two gamma spectrometers, a well Ge and a semi-planar Ge (HP), are now installed and calibrated for measurements of environmental radioactivity with special attention being paid to the requirements needed for aquatic mass-balance studies, including isotope-particle dynamics and dating of recent deposits. These facilities will complement the previously developed isotope dilution alpha spectrometry (PIPS detectors) and radon emanation (ionization chambers) techniques for 210Pb dating. A careful evaluation of efficiencies and background of the Ge detectors, together with the influence of the sample's intrinsic activity on the lower limit of detection (LLD), allowed us to study the relative importance of detector and shield specifications on low level gamma spectrometry of environmental samples with various sizes and composition.

An efficient quantitative technique for the simultaneous analyses of radon daughters 210Pb, 210Bi and 210Po

An improved and time efficient technique has been developed for quantitative determination of the long-lived 222Rn daughters ( 210Pb, 210Po and 210Bi) in atmospheric and oceanic samples. The sample is first spiked with yield tracers for polonium (208 or 209), bismuth (207), and lead (stable lead carrier). These nuclides may then be scavenged through iron hydroxide precipitation and redissolved in a dilute (pH ∼ 2) nitric acid plating medium with citrate and hydroxylamine hydrochloride at 90° centrigrade with constant stirring. First a silver planchet is suspended in the solution which plates polonium to high efficiency. Second, a nickel planchet is suspended in the same solution which is maintained hermetic ( e.g. bubbling with helium) and bismuth is plated next with high efficiency. Third, lead is purified from the same solution using anion exchange techniques and isolated for beta counting as the sulfate. Polonium is analyzed by isotope dilution alpha spectrometry. Bismuth and lead are analyzed by anti-coincident beta counting in a low level shield. In the case of bismuth, the 207 tracer is added in quantities at least comparable to the background of the beta system such that counting before and after the decay of 210Bi gives the bismuth yield. The unique characteristics of this technique are its speed and efficiency; all three radon daughters can be isolated for counting within 4 hr of pre-treating the sample. The remaining solution can be treated subsequently for other analyses as appropriate.

The determination of leachable uranium in marine and lacustrine sediments by steam digestion

Uranium can be leached with a mixture of nitric and perchloric acids from 1 g of marine or lacustrine sediment in an autoclave at 275° and 2 atm in 4 hr. The leachate resulted from this steam digestion may then be analyzed for uranium by isotope dilution alpha spectrometry with a precision of about ± 7%. In comparison to the conventional leaching scheme by wet digestion in an open beaker, this method is less time consuming, less labor intensive, requires the use of smaller amounts of acids while it yields data with comparable accuracy and precision. In the analysis of a set of samples collected from a variety of depositional environments, this method yielded results that were indistinguishable from those obtained by the conventional method.

On the capabilities of isotope dilution alpha spectrometry in the determination of plutonium concentration

The determination of plutonium in spent fuel solution by isotope dilution alpha spectrometry (IDAS) is described. Two aliquots of spent fuel solution were separately spiked with well characterized solutions of 238Pu and 239Pu. The pure spiked and unspiked plutonium solutions were obtained using a partition chromatographic technique. The alpha activity ratios of 238Pu(239Pu+240Pu) have been measured by alpha spectrometry and the concentration of plutonium calculated using isotopic composition data from mass spectrometry measurements. In parallel, the plutonium concentration was also determined by isotope dilution mass spectrometry (IDMS). The main aim of this experiment was to show the capability of IDAS compared to IDMS. Therefore the factors affecting the precision and accuracy of the IDAS method are discussed in detail. Also the outline of IDAS based exclusively on radiometric measurements (isotopic composition of plutonium by gamma spectrometry) is presented and its capabilities discussed.

Experimental evaluation of239Pu,238Pu and233U spikes for determining plutonium concentration by thermal ionization mass spectrometry and alpha-spectrometry

Experimental evaluation on the use of239Pu spike in Isotope Dilution-Thermal Ionization Mass Spectrometry (ID-TIMS),238Pu spike in Isotope Dilution Alpha Spectrometry (IDAS) and233U as a Non-Isotopic Diluent in Alpha Spectrometry (N-IDAS), for determing plutonium concentration in samples with burn-up values in the range of 1,000–10,000 MWD/TU is done. Precision is determined by analyzing replicate aliquots from different samples using each of the three spikes. Accuracy is established by comparing the results with those obtained by using well recognized spike242Pu in ID-TIMS. It is shown that the use of239Pu spike with the latest generation thermal ionization mass spectrometers gives the best precision (0.2%), whereas the precision values of 0.5 and 1% can be obtained by using238Pu and233U spikes, respectively, on a routine basis. Reasons for the difference in the precision values are discussed, along with the merits and drawbacks on the use of different spike isotopes.

Lead-210 chronology of the Scandinavian SWAP sites

In the Surface Water Acidification Project (SWAP) sediment profiles from five Scandinavian sites were analysed for 210 Pb by using refined isotope dilution alpha spectrometry. The 210 Pb parameters of these lakes were very similar to those obtained for protected forest lakes with no land-use activities. These data demonstrated almost exclusive atmospheric inputs and an internal deposition regulated by the organic fractionation and the grain-size distribution in the sediments. Preliminary speciation experiments showed minor losses of 210 (≤ 5%) through enhanced dissolution of fulvic compounds at acid conditions (pH ≥ 4). The sediment accumulation rates (constant rate of unsupported 210 Pb supply (CRS) model) of the lakes gradually increased, by at least a factor of three, over the past century although 210 Pb parameters did not show any strong signs of enhanced land-use activities. This is perhaps caused by more efficient preservation of the sediments through humic precipitation under more acid conditions.

Trace uranium analysis by isotope dilution alpha and mass spectrometry and comparison with other techniques

In this paper uranium determination by isotope dilution mass (MSID) and alpha spectrometry (ASID) using 233U as an isotope diluent is discussed. In addition, a new form of MSID employing two tracers ( 235U and 233U) is developed, where two independent uranium values are obtained for single dilution. The precision and accuracy of each technique are evaluated by comparison with other techniques like X-ray fluorescence and instrumental neutron activation analysis. The techniques, employed here for geological samples, can easily be adapted for environmental materials.

Isotope dilution alpha spectrometry with spike enriched in233U for the determination of uranium in geological samples

Isotope dilution alpha spectrometric /IDAS/ method has been developed for the determination of uranium in geological materials. The spike employed as uranium enriched in the isotope 233. The results of the analysis for rock and ore samples show that the precision and accuracy of the method are comparable to other analytical techniques and the method can be employed for routine analysis.